Internal combustion tool



June W, WW E. R. BODDINGHOUSE J A I INTERNAL COMBUSTION TOOL Filed Oct;15, 1937 Patented June 13, 1939 za i si.

INTERNAL COMBUSTION TOOL Emmons R. Boddinghouse, Ehic'ago, Ill.,assignor to Gas Tool Patents Corporation, a corporation of DelawareApplication October 15, 1937, Serial No. 169,277

to Claims. l (01. 123-41 Thisinvention relates to an internal combustionpercussive tool or hammer, and more particularly to an improvedarrangement for, returning the piston of a hammer of the free piston ayp One feature of this invention is that it provides improved operationand power; another feature of this invention is the provision of ahammer having such a predetermined relationship be- 10 tween therelative weights of the parts, the hardness of the parts and the springloading as will insure durability and most eflicient operation; yetanother feature is that the life of the return springs'and associatedparts is improved? other vl5 features and advantages of this inventionwill,

be apparent from the following specification and. the drawing, in whichthe figure is a vertical view, principally in section, of a completehammer embodying the invention hereinafter described.

: The hammer disclosed herein is an improve ment upon hammers of thefreepi'ston type, the general operation of which is already known in theart. The present application is a continuation in part of my applicationSerial No. 739,553,

25 filed August 13, 1934, which issued as Patent 2,101,608 on December7, 1937.

The hammer isof the internal combustion type wherein a cyl nder in has apiston ll freely reciprocable therein, the hammer operating on the 80general principles of a two stroke cycle internal combustion engine andbeing adapted to impart blows to a tool l2 through an anvil l3.

Additional'mech'anism and parts are provided associated with thecylinder l0 and piston l l to 35 form an operative internal combustionengine.

A combustible charge of air and vaporized gasoline, for example, issupplied from the chargeforming or fuel supply unit II to the chamber l57 beneath the piston, where it is partly compressed 40 by the downwardorworking stroke of the piston.

Near the bottom of this stroke the charge is transferred from. thesub-piston compression space to the combustion chamber at the top of thecylinder through the transfer passage Hi. The charge is 46 then finallycompressed on the upward stroke of the piston, effected by the returnspring means; and is ignited by the spark plug I! at the proper time, asa result of action of the circuit breaker or timing device U, whichdevice has. a movable 50 part driven by direct contact with a camsurface on the piston ll. Combustion of this charge drives the pistondownward on its'working stroke to strike the anvil l3 and transmit ablow to the tool when it is in the working position illustrated 65 'inthe drawing, the burned gases being discharged through the exhaust portI!) at the end of the stroke and the cycle then being repeated.

Handles 20 and M are provided to enable a workman or operator toproperly manipulate the hammer, to spot the tool on the working point,and to lift the .hammer between operations. Starting is accomplished bymanually depressing the starting rod' 22 until the piston is near thelower end of its travel, then releasing it so that the piston risesrapidly under the urging of the 10 return spring means and compressesand ignites a charge in thefiring chamber. The source of current forignition is attached to the spark plug H and the timer [8 by appropriatelead .wires,

brought into one handle of the hammer through 16 the flexible cable 23from an external source.

It will be seen that the hammer comprises a relatively longsubstantially cylindrical body having a bore extending therethrough fromthe top to the bottom, but being of somewhat different 20 diameters atdifferent parts. Thebody comprises the cylinder proper ill, the anvilhousing 21 and the spring housing 28. These are made as separate partsmerely for manufacturing and assembling convenience, and are allconcentric and 25 held rigidly together when the hammer is assembled; Itwill be understood that the important part is to have a long borecontaining the various parts, and "cylinder" will be used hereafter todefine this entire bore, rather than merely the firing chamber orcylinder proper.

The cylinder has mounted therein in its anvil housingportion, an anvilsleeve bearing 29. This sleeve provides a bearing for the anvil i3, andis a gas tight fit both with the anvil and with the 5 cylinder wall.This sleeve bearing is longitudinally movable in the cylinder, and itsuppermost position, as illustrated, abuts an annular shoulder or stopmember. -It will be noted that the anvil I3 is mushroomed out at thebottom to form ahead which limits the upward movement thereof. When thehammer is working the tool I2 is, as a result of pressure on the work,held upwardly in the hammer in the position illustrated. The full impactforce of .the piston blow may thus .be delivered. to the tool, since theanvil has a range of longitudinal motion before it strikes the partbelow it. a

Immediately beneath the sleeve bearing 29 and abutting it is thefollower 30. This follower surrounds the upper. portion of the tool I!and is axially or longitudinally movablein the housing 28. It issupported in a rest position against the sleeve bearing by the recoilabsorbing spring 3|, which the follower and its lower end abutting thebottom of the hammer. The follower also has a reduced portion lyingwithin the spring and movably mounted in the opening 32 at the bottom ofthe hammer, so that the follower is guided at each end.

The return spring means comprises a piston return spring 33 and aheavier surge cushioning spring 34 therebelow. The two springs contacteach other, and the upper end of the spring 33 abuts the bottom of thepiston ll, surrounding the striker portion thereof. In the operation ofthe device the piston is returned after the power stroke by the combinedaction of the springs 33 and 34 and the rebound which occurs from theimpactof the striker portion of the piston upon the reduced portion ofthe anvil. In order that the anvil and hammer may have the necessarydurability and may cause the desired rebound, they should each have aminimum hardness of 60 scleroscope or about Rockwell (1-44.

To describe the details of the hammer more fully, the particular hammerillustrated weighs about 91 pounds and delivers about 1450 blows perminute when. working. 'The piston II is about 2% inches in diameter andweighs seven pounds five ounces. It has been found that the weight ofthis piston should preferably be kept within a range of from four tonine pounds. piston, while it delivers more powerful individual blows,slows down the speed of the hammer so that the total work output is notas great; too light a piston, as for example a 3 pound piston in thissize hammer, results in high operating speed but again less work output.The return spring means are arranged so as to be under a maximum staticspring load of about '75 pounds when the springs are compressed untilthe striker portion of the piston is in contact with the top of theanvil II; that is, the maximum spring load referred to herein is thatforce in pounds required to force the piston manually down into contactwith the anvil. The piston return spring means should be relativelyweak, having an in crease in load of less than 50 pounds per inch ofcompression, and preferably even less than 25 pounds. The preferredembodiment described herewith has a piston return spring assembly whichincreases in load at about 16 pounds per inch of compression.

Not only is the relationship between the loading of the various springs,the rate of change thereof and the piston weightimportant, but also "thehardness of the anvil and the striker portion of the piston. I havediscovered that the mainte nance of a predetermined ratio between thepiston weight, the hardness of the striker portion of the piston and'ofthe "anvil, and the maximum spring load of the return springs isessential to efficient operation of the hammer as a whole. Thescleroscope hardness of the striker portion of the piston and the anvilpreferably should not fall below a. minimum of 60'scleroscope. Themaximum spring load in pounds of the return springs should not exceedthirty times the weight in pounds' of the piston. When these ratios aremaintained, the device will have the rigidity of action required for itswork and excessive vibration will not be imparted to the entire device.There is a close relation also between the spring load and the hardnessof the contacting parts. That is, if the anvil and striker portions aremade harder, the maximum static load of the piston return springs mustbe lower and vice versa. Normal engineer- 'achieve the desired results.

A heavier ing practice indicates hardening of parts subject .to impactto a Rockwell hardness of from 0-35 to about C-42. It has been found toresult in much better hammer operation and lessened spring troubles 'ifthe hardness of these portions is much higher than normal, at least aRockwell hardness of C-47 about 60 scleroscope). With such a hardnessthe maximum static spring load when the striker portion contacts theanvil should be kept less than 30 times the piston weight to While thehardness and spring loading within these ranges gives appreciablyimproved results over normal practice, the best combination has beenfound to be an anvil and striker portion hardness within the range fromRockwell 0-57 to C-63 and a return spring means load, when the strikercontacts the.

anvil, of from 8 to 15 times the weight of the piston. In' theparticular hammer illustrated herewith the anvil and striker portionhave a hardness of Rockwell C-60, and the spring loading is about 11times the piston weight.

Whatever the reasons, the particular spring hardness and weightcombinations described, and more particularly a loading of from 8 to 15times the piston weight, provide a distinctly better hammer underoperating conditions than those heretofore known. This arrangementcauses the hammer not only to run more smoothly and with more power whenworking, but also with an absence of excessive vibration at all times,even when lifted. providing a much more comfortable and easier handlinghammer for the operator than those heretofore used. yet sacrificing noneof the working power. The older type hammers produce quite a clatter andfrequent jumps when held up, with intense wracking vibration in thebody, noticeably absent in the hammer constructed in accordance with theprinciples set out above.

While I have described and claimed certain embodiments of my inventionit is to be understood that it is capable of many modifications.Changes, therefore, in the construction and arrangement may be madewithout departing from the spirit and scope of the invention asdisclosed in the appended claims.

I claim: 1. In an internal combustion hammer, a cylinder and a pistontherein, an anvil and means supporting it below said piston, returnspring means for returning the piston to firing position, the maximumload of said spring means when compressed by said piston until thelatter touches the anvil not exceeding thirty times the weight of thepiston, the anvil striking portion of the piston and the anvil having aminimum hardness of sixty scleroscope,

2. An internal combustion hammer of the character described. including:a cylinder; a piston freely reciprocable therein, said piston having astriker portion; an anvil adapted to receive blows from said striker andtransmit them to a tool when said tool is in working position, saidanvil and striker portion having a minimum hardness of Rockwell 0-44;means for supplying a combustible charge to said cylinder to effectdownward movement of said piston; and return spring means for returningthe piston to firing position, the maximum static load of said springmeans not exceeding thirty times the weight of the piston.

3. An internal combustion hammer of the character described, including:a cylinder; a piston freely reciprocable therein, said piston having astriker portion; an anvil adapted to receive blows from said striker andtransmit them to a tool when said tool is in working position, saidanvil and striker portion having a minimum hardness of Rockwell -44;means for'supplying a combustible charge to said cylinder to effectdownward movement of said piston; and return spring means for returningthe piston to firing position, the maximum static load of said springmeans being from eight to fifteen times the weight of the piston.

4. An internal combustion hammer of the character described, including:acylinder; a piston freely reciprocable therein, said piston having astriker portion; an anvil adapted to receive blows from said striker andtransmit them to a tool when said tool is in working position, saidanvil and striker portion having a minimum hardness of Rockwell C-44;means for supplying a combustible charge to said cylinder to eflectdownward movement of said piston; and return spring means for returningthe piston to firing Y position, the maximum static load of said springmeans being about eleven times the weight of the piston.

5. An internal combustion hammer oi the character described, including:a cylinder; a piston freely reciprocable therein and having a weight offrom four to nine pounds, said piston having a striker portion; an anviladapted to receive blows from said striker and transmit them. to a toolwhen said tool is in working position;

, means for supplying a combustible charge to said cylinder to eflectdownward movement of said piston; and, return spring means for returningthe piston to firing position, the maximum static load oi said springmeans being within the range of ircm eight to fifteen times the weightof the piston.

6. Ahammer of the character claimed in claim 5, wherein said piston hasa weight of about seven pounds. 5 a

7. An internal combustion hammer of the character described, including:a cylinder; a piston freely reciprocable therein; said piston having astriker portion; and an anvil adapted to receive blows from said strikerand transmit them to a tool when said tool is in working position, saidanvil and striker portion having a hardness within the range of RockwellC57 to 'C-63.

8. An internal combustion hammer of the character described, including:a cylinder; a piston freely reciprocable therein, said piston having astriker portion; return spring means for said piston; and an anviladapted to receive' blows from said striker and transmit them to a toolwhen said tool is in working position, said anvil and striker portionhaving a hardness within the range of Rockwell C-5'l to C-63, themaximum static load or said spring means being within the range of eightto fifteen times the weight of the piston.

9. An internal combustion hammer oi the character described, including:a cylinder, a piston freely reciprocable therein, said piston having astriker portion; an anvil adapted 'to receive blows from said strikerand transmit them to a tool when said tool is in working position, saidanvil and striker portion having a hardness of about Rockell C-fiO;means for supplying a combustible charge to said cylinder to effectdownward movement of said piston; and return spring means for returningthe piston to firing position, the maximum static load of said springmeans being about eleven times the weight of the piston.

10. A hammer of the character claimed in claim 9, wherein said pistonhas a weight of from four to nine pounds.

EMMONS R. BODDINGHOUSE.

